The current polyurethane based elastomeric fibers (spandex) provide acceptable stretch for some applications but unfortunately are not resistant to many textile processing chemicals and do not stand up well to industrial laundering conditions. They are also often difficult to incorporate into heavy bottom weight fabrics like denim.
To be used in durable fabrics, the fibers making up the fabric have to be, inter alia, stable during dyeing and heat setting processes. For an elastic polyolefin fiber to be stable under dyeing and heat-setting conditions, it is often crosslinked by one or more of a number of different methods, e.g., e-beam or UV irradiation, silane or azide treatment peroxide, etc., some methods better than others for fibers of a particular composition. For example, polyolefin fibers that are irradiated under an inert atmosphere (as opposed to irradiated under air) tend to be highly stable during dyeing processes (that is, the fibers do not melt or fuse together). The addition of a mixture of hindered phenol and hindered amine stabilizers usually further stabilized such fibers at heat setting conditions (200-210° C.).
Lycra®, a segmented polyurethane elastic material manufactured by E. I. du Pont de Nemours Company, is currently used in various durable stretch fabrics. Lycra, however, is not stable at the typical high heat-setting temperatures (200-210° C.) used for polyethylene terephthalate (PET) fiber. Moreover and similar to ordinary uncrosslinked polyolefin-based elastic materials, Lycra fabrics tend to lose their integrity, shape and elastic properties when subjected to elevated service temperatures such as those encountered in washing, drying and ironing. As such, Lycra® cannot be easily used in co-knitting applications with high temperature fibers such as polyester fibers.
Thus, there is a continuing need for heavy weight stretch fabrics which are resistant to many textile processing chemicals and are capable of surviving industrial laundering conditions including chemical and heat treatment.